The present invention relates to a new light source using electric discharges for producing weakly-ionized, low-temperature plasma of high density and large volume. Such plasma can be provided effectively in a stable state according to the present invention.
Conventional light sources for illumination radiate the light from filaments such as tungsten wires which are incandescently heated at an elevated temperature, and the light emitted from atoms, molecules or ions excited in a gas such as vaporized mercury, in which electric discharges appear.
The incandescent light has a good color rendering, but has not a good electric-to-optical conversion rate (or light producing efficiency).
The discharging type of light source works at an increased efficiency, but has a poor color rendering.
The quantity of electricity consumed for civil use is about 15% of the total quantity of electricity consumed in the world. Therefore, with a view to saving electric energy the development of the new light source has been directed mainly to the electric discharging type of light source, which is capable of producing the light at an increased efficiency.
Gas laser-devices in which gases are employed as a laser medium use excitation by electric discharges, particularly glow discharges.
However, the composition of the gas is limited, and the pressure of the gas at which the glow discharge can appear in a stable state is limited, also.
To increase the power and efficiency of the gas laser, it is necessary to excite the gaseous medium at an increased density by an external energy source, for an example, by a beam injection of high energy electrons.
Such equipment, however, is complicated in structure, and good maintenance of the equipment is required.
The gas laser produces the electric discharge of increased electric current, and accordingly the associated forced-cooling system is large in size.
As for a conventional optically-pumped laser, an arc lamp tube or xenon flash lamp tube is used for pumping a laser medium. For the purpose of increasing the light emitting efficiency, the lamp is placed at one of the focuses of an elliptical reflector and the laser medium is placed at the other focus of the elliptical reflector.
To increase the light emitting efficiency, and hence the output of such an optically-pumped laser it is necessary to encircle the laser medium by plural excitation lamps.
When the pumping lamps are made to turn on, their substantial portions are heated at an elevated temperature, and therefore, such pumping lamps and laser medium are put in water for cooling.
The optically pumped laser equipment, therefore, is complicated in structure, and is difficult in handling and maintenance.
Still disadvantageously pumping lamps are short in life, and inconveniently they cannot be changed without removing the laser medium.
A phase-controlled, multi-tapping ac power supply is known. It can provide a phase-controlled, ac power of low frequency, and is appropriate for use in producing an electric discharge of large volume (weakly-ionized, low-temperature plasma) in a stable state with low costs (see Japanese Patent Laid-Open No. H-8-330079). Also, an electrode assembly which is used with the phase-controlled, multi-taping ac power supply to produce an electric discharge at an increased efficiency is shown (see Japanese Patent Laid-Open No. H-10-130836). A method of establishing a multi-poled magnetic field is also known (see Japanese Patent Laid-Open No. H-10-134994).
The electrode assembly comprises a plurality of electrode pieces fixed to the cooled inner wall of the equipment via an intervening sheet of thermally conductive, electrically insulating material whereas the multi-poled magnetic field can be established in the vicinity of each electrode piece by a plurality of magnets, which are fixed to the outer wall of the equipment, thereby confining the plasma in the vicinity of each electrode piece.
One object of the present invention is to provide an electric discharging type of illumination apparatus which is capable of producing light of increased power, still saving the required energy. The illumination apparatus comprises a gas laser, a phase-controlled, multi-tapping ac power supply and an electrode assembly in combination. The electrode assembly is attached to the inner wall and the magnet assembly for establishing a multi-poled magnetic field is attached to the outer wall of the equipment.
Another object of the present invention is to provide a flash lamp simple in structure, easy in maintenance, and long in life, and is capable of working at an increased efficiency, and of providing an increased power of light.
To attain these objects a phase-controlled, multi-electrode type of AC discharge light source according to the present invention comprises: a plurality of electrode pieces arranged laterally and fixed to the electrode-application area inside of the electric discharge chamber with an insulation layer laying between the electrode pieces and the electrode-application area; multi-pole magnetic field establishing means provided outside of the electric discharge chamber to establish the multi-pole magnetic field on the surface of each electrode piece, thereby confining the electric discharge in the vicinity of the electrode piece; and a phase-controlled, multi-tapping ac power supply connected to the electrode pieces for producing light in the electric discharge chamber.
A phase-controlled, multi-electrode type of AC discharge light source is so constructed that it further comprises cooling means placed outside of the electric discharge chamber for cooling the electrode pieces.
A phase-controlled, multi-electrode type of AC discharge light source is so constructed that the electric discharge chamber has a light-transparent object placed ahead of the electrode pieces.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the electrode-application area is flat.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the electrode-application area is concave.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the electrode-application area is semi-spherically concave.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the electrode pieces are formed by printing and sintering an electrically conductive material onto the electrode-application area.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the electrode pieces are formed by plasma-spray coating an electrically conductive material onto the electrode-application area.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the multi-pole magnetic field establishing means comprises a thin magnetic sheet having a stripe pattern magnetized alternately with north or south pole, thereby establishing the multi-pole magnetic field on the surface of each electrode piece.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the multi-pole magnetic field establishing means comprises a plurality of magnet strips alternately magnetized in north or south pole, the magnet strips being laterally arranged closely to each other, thereby establishing the multi-pole magnetic field on the surface of each electrode piece.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the phase-controlled, multi-tapping ac power supply is a four-phase ac power supply.
A phase-controlled, multi-electrode type of AC discharge light source according to the present invention comprises: a plurality of electrode pieces arranged laterally and fixed to the electrode-application area of the inner wall surface of the electric discharge chamber with an insulation layer lying between the electrode pieces and the electrode-application area, the laser gas being circulated and cooled in the electric discharge chamber; cooling means for cooling the electrode pieces; multi-pole magnetic field establishing means for establishing the multi-pole magnetic field on the surface of each electrode piece, thereby confining the electric discharge in the vicinity of the electrode piece; and a phase-controlled, multi-tapping ac power supply connected to the electrode pieces for producing the light in the electric discharge chamber.
A phase-controlled, multi-electrode type of AC discharge light source comprises: reflection condenser mirror means placed outside of the laser medium, the reflection condenser mirror means having a light-transparent object placed on its front side, a plurality of electrodes laterally arranged on the surface of the reflection condenser mirror means to delimit the electric discharge chamber; cooling means placed outside of the electric discharge chamber for cooling the electrode pieces; multi-poled magnetic field establishing means for establishing the multi-poled magnetic field on the surface of each electrode piece, thereby confining the electric discharge in the vicinity of the electrode piece; and a phase-controlled, multi-tapping ac power supply connected to the electrode pieces for producing the light in the electric discharge chamber.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the reflection condenser mirror means is flat.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed that the reflection condenser mirror means is concave.
A phase-controlled, multi-electrode type of AC discharge light source may be so constructed according to claim 16 that the reflection condenser mirror means is formed on the inner wall surface of the circular cylinder.